|
Anonymous | Seeing that the NAD and Rotel hum and I have seen it said it is because of a lack of filters to get better sound, I was wondering if the Arcam has the same problem. |
|
Anonymous | Actually I should have said hum or hiss. |
|
Gold Member Username: ArtkAlbany, Oregon USA Post Number: 1882 Registered: Feb-05 | I haven't heard any hum from the Arcam but I may going to Portland this weekend and if I do I will give it another listen. Your reasons for the hum are accurate as I've been told by folks who work on this stuff all of the time. |
|
Gold Member Username: Edster922Abubala, Ababala The Occupation Post Number: 2460 Registered: Mar-05 | > a lack of filters to get better sound, So you guys mean that NAD engineers may have decided that the hum/hiss was a worthwhile price to pay for better overall music dynamics? Interesting! Aaron the sales rep from my local shop where I bought my Marantz said something along those lines about the Marantz 5400 cdp compared to mass-market CDPs made by the likes of Pioneer which he said had fewer mechanical issues but at the cost of lower music quality. He seemed to imply that from an engineering and economic standpoint, you can have gear that provides top notch music quality but at the expense of some compromises in long-term mechanical durability, or vice versa, but not both unless it was extremely high end stuff. I hope that the more-experienced audio folk here like Art, Jan, and Tawaun will comment on this theory... |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 6000 Registered: May-04 | That theory makes no sense. I think. Since this is now second hand information, I'm not certain what the intent of the original statement might have been. If the sales rep meant to say budget equipment cuts corners where expensive equipment can use whatever the designer chooses. Then I agree. Cost no object designs are just that. Though that hardly guarantees reliability. The audio world is full of products that fit all categories of generalization. Over the years there have been many highly successful and well regarded products which came in at budget prices. One of my favorites was the Superphon pre amp. Very simple with minimal parts. It had terrific sound but couldn't keep running for any length of time. Being a budget product, people finally got tired of having it in the shop instead of in their system and gave up on repairing the unit. The company went under and then no longer could supply parts. That finished off the Superphon pre amp. If you have access to a Stereophile recommended components list from the early '90's, look for the number of manufacturers which are still in business. On the other side is the original BK ST-140. A very simple design, it had little to go wrong and there should be a fair number of ST-140's still running. Being a budget design, however, it was set to give its best sound when used with fairly benign loads of 8 Ohms. Lower impedance speakers did not do well with the ST-140. But even when used with a simple speaker load, the higher priced BK products of the time were more reliable. Why? Mostly because the higher priced products were more forgiving of reactive loads. There were more output devices and they were run farther from their limits. On the high priced side, you have more than enough products which have failed because they were so tightly toleranced the product couldn't broach any deviation from the expected operation schedule. More than a few amplifiers will have their outputs biased so close to the limit of acceptability that any deviation in the operating conditions causes havoc. Just simple line voltage variations can do in a design that teeters on the brink of disaster. Many companies have excellent designs and yet choose the wrong parts. A 400 volt cap in a tube amp with 450 volt bias supply will last just long enough to get a good review. For quite a long time, the model of an amplifier was one that could drive Apogee Scintillas at less than 1 Ohm. The amplifier had to be capable of arc welding to accomplish this task. For years, the review magazines of the high end had products that crapped out during the review period. This extended to all areas of a system, not just the amplifier. The original Quad speaker was wonderful as long as you didn't ask too much from it. Cantilevers on cartridges collapsed at an alarming rate. And, finally, there are companies which consistently turn out good sounding, highly reliable gear for decades. Most of them are not budget oriented unless you consider the budget to be over twenty years of use. Go figure. |
|
Silver Member Username: Frank_abelaBerkshire UK Post Number: 932 Registered: Sep-04 | If the Arcams hum I haven't noticed. They use toroidal transformers so it's possible that dirty mains could make them hum if there's no filter in there. Naim Audio make some of the most reliable kit in the business. Most of the bigger more expensive models hum. This is because Naim, like NAD, refuse to use filters which kill the sound but also transformers which don't hum but which don't sound as good as transformers which do hum. Naim kit also hisses more than other kit that is just as expensive. The hiss only intrudes when there is no signal typically. This is not cheap kit with their range of 2-channel amps being between $1500 and $40k, and generally recognised as a strong competitor in this rarified field. And yet it hums! Hum is mainly caused by dirty mains supply. If a device, possibly in another house even, dumps noise into the circuit, this can be passed into the transformer of your amplifier which could then resonate depending on the noise. Some of the worst offenders are switched mode power supplies such as found in computers. When this happens it is not a problem or fault on the part of your amplifier but on the part of the noisy mains supply and that cursed device. This is why it's a well known upgrade to introduce a high current separate spur dedicated to your system into your abode's electricity circuit. A separate spur fitted with a 30 amp fuse allows your hifi to breathe better, rendering better dynamics and resolution as a minimum. You may still get some hum or noise, but it is usually less so through a separate spur (no DIY please - get an electrician to do it). Regards, Frank. |
|
Gold Member Username: T_bomb25Dayton, Ohio United States Post Number: 1082 Registered: Jun-05 | Nowadays you have to look at companies stability as a company,have they changed distributors or price cuts or so on.Most companies are out for the dollar no matter how much we respect them and garner their products.Look at AR for instance once a mainstay and a inovator in the audio world,and not to mention the originators of the softdome tweeter,well them and Phase Technology will surely argue this PT formerly known as the US Speakers in the 50s and 60s.AR a once prominant name in audio has been thru more changes than Micheal Jackson has had nose opperations,are hardley heard from now their qaulity has dropped signifantly and they are hard to find now.Monitor Audio once the biggest cabinet makers in the industry at one time they built cabinets for over 120 speaker companies in England and many more around the globe,their flagship used to cost $12000 now it costs $4000,and I've heard both speakers no comparrison.You have to watch what companies do,will they skimp on cheaper parts? you bet most will.Always read about a companies history and where are they now compared to yesteryears you will come up with a lot of answers on your own,that they will never tell you. |
|
Gold Member Username: Edster922Abubala, Ababala The Occupation Post Number: 2465 Registered: Mar-05 | Frank, so do you think that this ultra-high-fidelity hum MIGHT be eliminated or at least reduced by expensive power conditioners which don't have much effect on lower end gear? |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 6006 Registered: May-04 | When we talk about hum we have to distinguish between mechanical hum from a transformer which vibrates excessively and electrically induced hum which may come from a poorly shielded transformer, poor component layout or from other system induced conditions. Hiss is another matter and is generally related to the design of the component in question. There is not much that can be done about hiss if it is designed into the component. Hum can be generated into the system by dissimilar ground potentials between various components. It can occur because of poor grounding in one component (star grounding techniques work well to ameliorate this situation) or as the result of connectiong two or more components with different ground potentials (star grounding of the system to a true earth ground can often solve, or lessen, this problem). A simple matter of how the connectors are grounded to the chassis can cause hum in a system. This is why you see cables with a direction indicated. The ground connection in the cable is made only at one end (usually the source end). On low end equipment you will find buffering circuits, capacitors, some poorly designed global feedback loops and so on that are meant to reduce the possibility the product will not operate well with other mass market gear. Most high end manufacturers will not use these circuits or components because they do affect the the sound quality. Unfortuantely, companies such as NAD make an assumption they are being sold by specialty shops which might understand how to make a system work well. Most unfortunately, this isn't always the case. I've never had a problem with NAD gear making noises through the system. I don't doubt that some people have; but I wonder how many of those complaints could have been solved with a little work on replacing components not well suited to the NAD or researching ground loops. As to whether the Arcam gear suffers from this problem, I have no answer, since I see this as most often system dependent if the problem is not mechanical hum from the tansformer. |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 6008 Registered: May-04 | "so do you think that this ultra-high-fidelity hum MIGHT be eliminated or at least reduced by expensive power conditioners which don't have much effect on lower end gear?" Frank is more than welcome to answer this question also, but my experience has been any inexpensive (read less than $1k) line conditioner will probably have a deleterious effect on the sound if it is designed to eliminate 60Hz ground fault noise. If you step up to a large, expensive power line conditioner with massive transformers and storage caps, you have, in effect, replaced that portion of the power supply in your equipment. The use of well made transformers and storage/filter caps will eliminate the 60 Hz component if it is line induced. Plugging all components into one dedicated circuit (the power line conditioner with common [star] ground points) will place everything at the same ground potential if the electrical ground of the main circuit the line conditioner plugs into is good. This will not remove mechanical hum from the transformer. However, many transformers hum because of problems in the line voltage. If these are eliminated by the filter caps or transformers in the line conditioner, the problem will be lessened. Most lower end gear can't tell the difference a line conditioner makes because of the poor power supply design and layout employed in low end gear. |
|
Gold Member Username: T_bomb25Dayton, Ohio United States Post Number: 1087 Registered: Jun-05 | Jan so where would choke regulators fit in to all of this?Musical Fidelity uses them to great affect,and its the quitest gear I've heard,but others have tried to use them and failed because they imposed to much on the sound quality.So why have everyone elses attempt to use them have been so unsuccesful? |
|
Gold Member Username: ArtkAlbany, Oregon USA Post Number: 1887 Registered: Feb-05 | Jan I've never had a problem with the 2 channel NAD gear, it's the multichannel products that have the issue. I've tried nearly everything to fix it and nothing improves it. My old Rotel AVR had the same problem. |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 6010 Registered: May-04 | Tawaun, chokes are an old fashioned design from the days of tubes. My McIntosh tube amps use chokes in their power supply. My understanding of what a choke accomplishes, and I am going on what I have been told on this one, is the same as an inductor in line in a speaker XO. A power supply filter capacitor is meant to take out the low frequency, 60Hz, AC ground noise. In this case the cap also works as we assume a parallel capacitor will in a simple first order XO; it filters any signal beneath it's shelf frequency. As the incoming AC is rectified to a DC voltage, there is substantial ripple in many power supplies. If this manages to make its way to the DC voltage it will affect the cleanliness of the DC feed going to the gain stages. The ripple is made up of higher frequency components of the AC voltage and cannot be filtered efffectively by simple capacitors. Here is the point where an inductor (choke) is useful. As in that same first order XO, the inductor/choke is placed in the final output stages of the power supply in order to smooth and filter any ripple from the out going voltage. Why chokes have fallen out of favor is primarily a function of solid state technology not needing the same high voltage DC feed to the gain stages. A tube amp is more susceptible to ripple as its requirements for voltage conversion are substantially more complex and demanding than most solid state designs. In current design a solid state rectifier is typically used and it is meant to filter out any ripple from the outgoing voltages. Most designs in the low to moderate price range, however, will have some amount of ripple that is present on the modulated signal passing through the amplifier. To get away from this ripple, some designers have used battery powered power supplies which supply only DC voltages from the get go. So the inductor/choke is meant to remove and smooth the final output of the power supply voltages. But, again as in a first order XO, adding the choke in line with the power supply will raise the impedance of the power supply. Increasing the impedance of the power supply will have a deleterious effect on the available voltage and, most importantly, current delivery when the amplifier has to produce large, immediate swings in wattage to accommodate a big bass note or the entire brass section giving it all they have. So chokes fell out of favor since solid state is not as susceptible to ripple effects as tubes and solid state rectification can eliminate most of the ripple. What MF has done is revive the choke to give the cleanest, quietest signal they feel they can manage. From what I remember the chokes are used only on the big 500 and 1,000 watt amplifiers and the NuVista designs. The NuVista is a variant of tube technology and operates very much like a tube in most respects. So a choke would be normal in that circuit and I believe is where MF initally revived the choke filter in the power supply. I can only assume the power supply is designed with a large margin of excess in the solid state amps. Like everything else in audio, a choke has advantages and disadvantages. Designing around a choke is not inexpensive. As with power and output transformers, not many companies can do excellent inductors and when they are used, they are expensive. The advantages of a choke in the final stages of the power supply amount to a cleanliness that rivals battery powered units while not having to deal with the constantly dwindling amount of power available from a battery. That's my understanding of chokes in a power supply. If anyone has a more "engineered" explanation, I would very much like to read what exactly the choke does. http://depalma.pair.com/Analog/analog.html You can also see the application of a choke in automotive audio in order to filter alternator noise from the volatge lines. The audibility of the choke in a car's environment is minimal and it serves the function well without being obtrusive. |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 6012 Registered: May-04 | Art - I have little experience with NAD AV gear. They were not producing AV receivers for the short while I sold NAD in the 80's. But, I have had no problems with the NAD AV receivers I own or have installed in friends homes. I gather this is a model dependent problem. If the problem exists with nothing but the speakers connected (no powered sub) to the receiver and all inputs open, then the problem is in the design of the equipment. I wouldn't doubt that NAD might have problems in this area as the more channels you pack into one box, it becomes increasingly likely there will be different ground potentials within the reciever. If the problem does not exist with just speakers connected and only shows up when other components are added, the problem is in the different ground potentials of all the equipment and how they are grounded to one another through the interconnects. This is a fairly common problem in consumer audio as all equipment has its own chassis ground and often a two pin AC plug putting ground and nuetral at the same potential. This is unlike pro audio where most equipment is grounded through the rack to a dedicated ground. Also many consumer audio designers design as if there are no other products that will ever be used with their equipment. Ground lifts, reversing the Ac plug, star grounding and changing the interconnects can often solve this problem. This company makes some in line ground lifts which might solve some problems. Unfortuantely, grounding problems are often a "suck it and see" situation where you can only try various remedies until you find what works. http://www.hlabs.com/technical/crossovers/ |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 6050 Registered: May-04 | Reading again my explanation of a choke regulator in a power supply, I think I put too much emphasis on just the AC ripple that filters into the DC supplies. One of the more common reasons for a choke today is filtering the remaining line noise from the power supply. The electromotive interference in most AC lines where a common transformer on the pole in the alley is shared by muliple households has a tremendous amount of noise on the AC line. This comes from refrigerators, air conditioners, computers in the same house and most large appliances. There's not much that can touch all that noise once it is in a power supply. Plenty of AC line conditioners at even a modest amount will incorporate a choke in the output to the system in order to squelch this line noise. The MF line has revived the choke regulators not only to deal with AC riple but also to deal with the noisey environment our electronics live in today. |
|
Gold Member Username: T_bomb25Dayton, Ohio United States Post Number: 1102 Registered: Jun-05 | Jan they use it in every every line and every peice of gear except for the X-Ray series.Sometimes I wonder if it hinders their dynamics,because comparing the 3.2 series to the X-Rays,the 3.2s are certainly not as dynamic as the X-ray,one of the resons that turned me to the Unison Unico intergrated Amp until the new X-Rays came out.The Chokes deffinetly make them more quite,but I wonder just how much its imposing or better yet diminishing the dynamics of MF gear.Antony Michealson claimed to have came up with a more cost effective way to take the role as the choke regulator in the X-Ray series,and it works its as quit as the other units but with a little more body and jump factor.Even the Kilowatts give this impression of being just a little to tame with just to much control over the speakers. |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 6083 Registered: May-04 | Like I said, the choke is going to raise the output impedance of the power supply. Unless the design is then accompanied with a further reduction in the input impedance of the various stages of the amplifier, the higher output impedance will have some effect on the ability of the gain stages to instantaneously draw voltage and current when needed for large scale transients. There are work arounds to this with lots of capacitance in the power supply reserves and multiple small caps instead of large storage capacitors. But there is nothing that changes the way the power supply works until you get to the switching power supplies, which have not proven successful in large wattage amplifiers. As with anything I'm aware of in audio, there is no free lunch. I used to tell my clients, "If the designer gives you one thing, they are likely to have taken away two." It is a series of trade offs no matter how you go about the design. With the enormous power reserves of the 500 and 1k watt amplifers, the feeling is probably there is more than enough power on hand for large scale transients. In the other components in the line, as with the amplifiers, the design was likely intended to go for low level detail by lowering the noise floor of the components. If large scale speed suffers slightly, that's the trade. You get one and I take one. That's pretty much how it works. I've not heard any of the MF gear and only know it from the write ups which have all been favorable. While Sam Tellig claims Michaelson is a vocal proponent of massive amounts of power, Tellig has stated he prefers his 2 1/2 watt single ended triode amplifier on many ocassions. It is not at all uncommon, in my experience, for the smallest amplifier in any company's line to sound sweeter and cleaner and basically just more musical than the very high wattage gear with similar design topology. The Adcom line is clearly this way. Some people claim the further the design gets from single ended, the worse the amplifier sounds due to the additional gain stages and the inability, at virtually any price range, to absolutely match two output devices, whether solid state or valve, to one another. When the signal is handed from one positive going device to another single negative going device, the variance between the two is minimized. When the signal is handed from three or four positive going deveices in a high wattage amplifier, to the same number of negative going devices, the chances of errors and discontinuities are increased expotentially. To some extent, you could say there are two types of audiophiles. Those who prefer low wattage amps for their sweetness and those who like the punch and control of lots and lots of watts. That would be a gross oversimplification; but you could say that. |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 6084 Registered: May-04 | BTW, if I remember the Unison product correctly, it uses just one output MOSFET for each side of the push pull output stage. Correct? |
|
Gold Member Username: Edster922Abubala, Ababala The Occupation Post Number: 2513 Registered: Mar-05 | > In the other components in the line, as with the amplifiers, the design was likely intended to go for low level detail by lowering the noise floor of the components. > To some extent, you could say there are two types of audiophiles. Those who prefer low wattage amps for their sweetness and those who like the punch and control of lots and lots of watts. Would it be wrong to make the rough generalization/oversimplification that solid state analog amps especially as compared to low-wattage tubes, that the higher the power the higher the noise floor? I don't know anything about tubes, but I had the impression some people find them desirable due to their warmth and musicality rather than low noise. |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 6089 Registered: May-04 | The amount of noise though any circuit, tube or solid state, will be determined by the circuit topology and the parts chosen. My Mac tube amps are dead quiet through 84dB sensitivity LS3/5a's. When connected to a pair of 104 dB Klipschorns, there would probably be quiescent noise even at idle. The tubes I have used over the past twenty five years of owning the amps have been somewhat quieter and somewhat noisier than each other; the better sounding the tube, the quieter it has been, in general. The same rules apply to solid state. It is difficult to get high gain without adding some noise to the amplifier's output since more gain generally means more circuits for the signal to pass through or the individual components are pushed further towards their limits. As an example, my Macs are rated at 40 watts per channel in stereo while a Dynaco Stereo 70 is rated at 35 watts per channel. The Macs use three gain stages before the output tubes with each stage run at a very conservative level. The important components in the signal path, as spec'd from McIntosh in 1962 (!), were 1% tolerance. The Dyna utilizes one gain stage pushed harder with internals spec'd at an average of 10% tolerance. Both distortion and noise are generally higher on the Dynaco. By taking each stage closer to its limits, the inherent noise of each preceding stage is amplified as much as the signal and then the noise of that stage is added to that amount of noise and so on. Add to that though, the Dyna sold for well under $100 and the Mac's sold for almost four times that amount. Four times the budget can get you a lot of performance differences. It is a trade off in that the Mac is a more complicated circuit than the Dyna. On the other hand, the Macs, by running each component more conservatively, have proven to be a quieter, cleaner and ultimately more reliable cirucit than the Dyna. It must also be said the Macs run in what is called a Unity Coupled output configuration (at the time an exclusive to McIntosh) while Dyna was the originator of the UltraLinear circuit. The two topologies also account for some of the difference in performance. |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 6090 Registered: May-04 | As to the "sound" of tubes vs. solid state, it is an on going debate whether one technology can be described as warm or cool. It is a matter of the devices chosen. To everyone who feels tubes are "warm", I would say maybe transistors are "cold". To everyone who thinks tubes are rolled off at the top, I would suggest solid state is too bright. One of the first set of replacement tubes I purchased for the Mac amps was marketed by a company called Groove Tube which sold primarily to musicians who value what tubes can do. The output tubes were sold in varying degrees of "hardness" and "softness" with the harder tubes distorting earlier and sounding (supposedly) more like solid state. The softer tube ratings indicated a tube which distorted more like a classic tube amp and had a more "mellow" tone and what was considered by all to be the classic tube midrange glow. In a tube amplifier with adjustable bias settings for the output tubes, you can adjust, to some extent, how the tube sounds by adjusting the bias going to the tube. You can also change the sound of a transformer coupled tube amp by using the different taps from the output transformer. Additionally, there are plenty of tube listeners who will tell you each time you add another gain stage to the tube itself, from triode, to tetrode to pentode to beam power design, you get further away from the "sound" of tubes. |